The Principle of Polysaccharide Gels

Abstract

For several decades attention has been directed to natural polysaccharide gels and synthesized polymer gels. The structure-function relationships at molecular level in water of polysaccharides, κ-carrageenan, ι-carrageenan, agarose (agar), and gellan family of polysaccharides (gellan, welan, rhamsan, S-657, deacetylated rhamsan and native gellan gum), which are industrially useful polysaccharides extracted from family of red seaweeds and bacteria, in principle are discussed on the view point of rheological aspects. The polysaccharide molecules (0.1% -1.0%) play a dominant role in the center of the tetrahedral cavities occupied by water molecules (99.0% -99.9%), and the arrangement is similar to a tetrahedral structure in a gelation process. The cage and hydrophobic effect play thermal dynamically dominant role in gelation process which gives lowest entropy to electrons of sugar residues. Though the chemical structure of these polysaccharides similar each other, their rheological (gelling) characteristics are quite different. Many investigations about the gelling properties of the polysaccharides have been undertaken to elucidate the structure-function relationship, but no other researchers have established mechanism at the molecular level. There is consistency in our investigations. Thus, the rheological analysis is one of significant methods for understanding the structure-function relationship of polysaccharides in aqueous media. The discussion provides many important information not only in academic field, but also in industrial one, such as food, cosmetic, pharmaceutical, drug delivery and tissue industries, and biotechnology.

Rheological Behavior and Pharmaceutical Applications of Bacterial Exopolysaccharides

“…At moderate concentration of sodium hydroxide, curdlan becomes completely soluble and assumes the structure of random coils. Similar ordered conformation is also observed when curdlan is added to other non-solvents such as 2-chloroethanol, dioxan or when water is added to dimethyl sulfoxide solution (Roca et al, 2015;Tako et al, 2016;Tako, 2015).…”

“…Apart from hydrogen bonds, van der Waals forces of attraction, ionic interactions or electrostatic forces of attraction also contribute to the phenomenon of gelation. Intramolecular linking may also be responsible (Tako, 2015).Two nongel-forming polysaccharides may form a gel due to synergistic action of the optimum concentrations of the individual polysaccharides (Wingender et al, 2012). It has been observed that linear, ionic homoglycans can readily form gels due to association at several junction zones.…”

“…Hydrogen bond formation between the solvent molecules and polymer-solvent molecules led to ice-like structure and finally transition from liquid to gel state. L-rhamnosyl residues in deacetylated rhamsan participate in gel formation (Roca et al, 2015;Tako et al, 2016;Tako, 2015). Curdlan with higher degree of polymerisation (approximately DP of around 200) exhibited gel formation on heating.…”

The Novel Pyruvated Glucogalactan Sulfate Isolated from the Red Seaweed, <i>Hypnea pannosa</i>

“…We also proposed gelatinization and retrogradation mechanism of amylopectin [36]- [38] and starch [39]- [44]. Tako realizes that there are some basic rules in gel-formation process including water molecules in principle [45]- [47].…”

A Novel and Facile Nanoclay Aerogel Masterbatch toward Exfoliated Polymer‐Clay Nanocomposites through a Melt‐Mixing Process

“…KC is capable of forming thermoreversible gel with gelation upon cooling and melting upon heating [37]. Moreover, KC exhibits a negative charge when dissolved in water; thus, the negatively charged system benefits to preserve the extended clay galleries (swollen state) of the PEGintercalated nanoclay during the transformation from a dispersed liquid to gel without penetrating the KC chains into a layered silicate spacing [38]. Minimal KC concentration of 1 wt.% was reported to create sufficient gelation on cooling [39][40][41].…”